For instance, JPH11-146616A (corresponding to U.S. Pat. No. 6,057,621) recites an electric motor, in which a stator is clamped by two frames in an axial direction of the motor. With this construction, a required precision can be lowered in comparison to a case where the stator (more specifically, a stator core) is press fitted or shrink fitted into a cylindrical housing. Thus, the manufacturing of the electric motor is eased.
A fastening method for fastening the respective frames of the above electric motor may include inserting a through bolt through corresponding holes of the frames on a radially outer side of the stator while holding the stator between the frames and thereafter fastening the frames together by tightening the through bolt, so that movement of the frames away from each other in the axial direction is limited. However, when this fastening method is used in a case where a circuit board, which includes a control circuit, is provided to one of the frames, the frame, to which the circuit board is provided, may possibly be deformed upon the tightening of the through bolt to cause a damage of the circuit board, thereby possibly resulting in a start failure of the electric motor.